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IrisVision was an expansion card developed by Silicon Graphics for IBM compatible PCs in 1991 and was one of the first 3D accelerator cards available for the high-end PC market. IrisVision was actually an adaptation of the graphics pipeline found in the Personal IRIS workstation to the Micro Channel architecture and consumer ISA buses found on most modern PCs of the day. It is also notable for being the first time that any variant of IRIS GL was ever ported to the PC (an experience that subsequently led to the creation of the OpenGL API).


In 1988, Silicon Graphics introduced the MIPS-based workstation computer, the Personal IRIS series. A few years later, IBM licensed both the graphics subsystem and the (then new) IRIS Graphics Library (IRIS GL) API for their RS/6000 POWERstation line of POWER1-based workstations. IrisVision was an unintended offshoot of SGI's attempts to port the subsystem to IBM's Micro Channel Architecture. They found it was much easier to debug the prototype implementations on an IBM PS/2.

To quote R.C. Brown:

"At some point, the light went off in someone's head; "Why don't we sell this board set for use in PCs?". IrisVision was born. Initially, the MCA card was re-designed to offer some features critical for the PC market, including standard 15-pin VGA-style video output and a 15-pin VGA passthrough input connector. The IBM genlock connector was moved to the top of the card, and stereo display signals were also brought out to the VGA passthrough connector. The card occupied 1 32-bit MCA slot and an adjacent 16/32 bit slot. One or two daughter boards provided framebuffer and z-buffer memory.
Work then began on the design of an Industry Standard Architecture (ISA or AT-bus) version of the card. It would occupy 2 16-bit ISA slots and use the identical daughter cards as the MCA (and IBM) versions of the board set."


Not unlike its Personal IRIS variant, IrisVision was capable of handling 8-bit and 24-bit raster images with a 24-bit Z buffer. The difference lay in that all this was integrated with a fifth generation Geometry Engine without having to upgrade the cards themselves. Around the same time, SGI was preparing to introduce the next series of graphics cards for their IRIS Indigo workstations, called "Express Graphics", which came in two variants for the Personal IRIS: Turbo Graphix and the Elan Graphics pipeline, both of them an evolution of IrisVision.

It came packaged with a proprietary 32-bit C compiler in order to take advantage of the 80386 and 80486's 32-bit extensions (at this time, SGI was moving forward to 64-bit microprocessors on their own platform). The PharLap 32-bit DOS-Extender was also packaged to further enable the use of large amounts of memory (up to 2 GB). Due to the nature of the pipeline, all execution calls to IRIS GL were displayed in fullscreen (MS-DOS could not display windows, so this left programmers with the freedom to write up their interface in pure IRIS GL).

The forgotten 3D revolution[edit]

3D graphics hardware was a relatively new prospect for microcomputers at the time, and was unknown in the IBM personal computing world. 3D graphics software was mostly associated with PowerAnimator and Softimage or niche applications on the Amiga 3000, such as Video Toaster and Lightwave, or the Macintosh Quadra, such as StrataVision, and 3D graphics hardware was frequently associated with UNIX machines. In contrast, in the IBM personal computing world, VGA was just barely coming into the spotlight when IrisVision came out on the market. IrisVision presented an alternative few had ever imagined on the Intel platform: that of a 3D platform that used MS-DOS as the base operating system.

AutoDesk quickly realized that they could capitalize on this graphics subsystem and released their most successful CAD and 3D production products with support for this card, among them AutoCAD (Revisions 12 and 13) and 3D studio 2 through 4. Eventually support for Microsoft Windows would be developed but without much ado as hardly any software on the GUI system would take advantage of the card.

Despite all this, IrisVision fell into relative obscurity, as IRIS GL hadn't reached its pinnacle as the de facto 3D API then was PHIGS, and few people had any real idea of what to do with 3D graphics (outside of the CAD industry). Another attempt to port SGI hardware to the PC platform would not occur until the introduction of the SGI Visual Workstation.

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